Improve Symbol information in Block IR

[ChingLongTin]

This adds more types of Symbols to Block IR, and addresses both comments in #355.
#355 (comment): we now require :ftc to be enabled for functions with multiple parameter lists
#355 (comment): we collect all class definitions during compilation into defnMap so that we can retrieve the definition for desugared classes generated from :ftc

In the future, we will need change StagedSymbols.mls to show that we have staged the Symbols correctly.
Instead of relying on the printout from showBlock, we probably will need to print the global map of created symbols, since showBlock will be used for pretty-printing code for the next stage and will not show a difference between the different types of symbols.

[LPTK]

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[Copilot]

Pull request overview

This PR enhances Block IR symbol fidelity (introducing distinct symbol variants like VirtualClassSymbol, ClassSymbol with richer metadata, and ModuleSymbol) and updates the staging/instrumentation pipeline to support these richer symbols, including stricter handling of multi-parameter-list functions via :ftc.

Changes:

• Extend Block IR symbol model and adjust pretty-printing to rely on symbol toString().
• Update Scala instrumentation to emit richer symbol objects and to pre-collect class definitions (defnMap) for later lookup.
• Refresh/add staging golden tests and extend Shape primitive-type handling (adds TypedArray).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
hkmc2/shared/src/test/mlscript/block-staging/StageSymbols.mls	Adds coverage for richer symbols and :ftc error behavior in staged output.
hkmc2/shared/src/test/mlscript/block-staging/Functions.mls	Updates golden outputs for new symbol formatting and :ftc behavior.
hkmc2/shared/src/test/mlscript-compile/Shape.mls	Extends primitive-type checks to include TypedArray.
hkmc2/shared/src/test/mlscript-compile/Block.mls	Updates Block IR model for richer symbol types and simplifies symbol printing.
hkmc2/shared/src/main/scala/hkmc2/codegen/Lowering.scala	Switches instrumentation entrypoint to applyBlockFinal to build defnMap before staging.
hkmc2/shared/src/main/scala/hkmc2/codegen/Instrumentation.scala	Implements richer symbol emission, defnMap collection, and :ftc enforcement for multi-parameter lists.

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